A search for the optical counterpart of the luminous X-ray source in NGC 6652

被引:16
作者
Deutsch, EW [1 ]
Margon, B [1 ]
Anderson, SF [1 ]
机构
[1] Univ Washington, Dept Astron, Seattle, WA 98195 USA
关键词
globular clusters : individual (NGC 6652); stars : neutron; ultraviolet emission; X-rays;
D O I
10.1086/300512
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We examine images of the held of X1832-330, the luminous (L-x similar to 10(36) ergs s(-1)) X-ray burst source near the center of the globular cluster NGC 6652, in order to identify the optical counterpart for further study. U and B ground-based images allow us to set a limit M-Bo greater than or similar to 3.5 for the counterpart at the time of those observations, provided that the color is (U-B)(o) similar to -1, similar to the sources known in other clusters. Archival Nubble Space Telescope observations survey most, but not all, of the 1 sigma X-ray error circle and allow us to set limits M-Bo > 5.9 and M-Bo > 5.2 in the Wide Field Planetary Camera 1 (WF/PC-1) and Wide Field Planetary Camera 2 (WFPC2) regions, respectively. In the WF/PC-1 images we do weakly detect a faint object with UV excess, but it is located 11." 7 from the ROSAT X-ray position. This considerable (2.3 sigma) discrepancy in position suggests that this candidate be treated with caution, but it remains the only reasonable one advanced thus far. We measure for this star m(439) = 20.2 +/- 0.2 and m(336) - m(439) = -0.5 +/- 0.2 and estimate M-Bo = 5.5 and (U-B)(o) = -0.9, similar to other known optical counterparts. If this candidate is not the identification, our limits imply that the true counterpart, not yet identified, is probably the optically faintest cluster source yet known or, alternatively, that it did not show significant UV excess at the time of these observations. Finally, we assess the outlook for the identification of the remaining luminous globular cluster X-ray sources.
引用
收藏
页码:1301 / 1307
页数:7
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